Group 3 and 4 metal alkyl and hydrido complexes containing a linked amido-cyclopentadienyl ligand: “constrained geometry” polymerization catalysts for nonpolar and polar monomers |
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Authors: | Stefan Arndt Klaus Beckerle Kai C. Hultzsch Piet-Jan Sinnema Peter Voth Thomas P. Spaniol Jun Okuda |
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Affiliation: | Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, D-55099, Mainz, Germany |
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Abstract: | In order to understand the nature of the putative cationic 12-electron species [M(η5:η1-C5R4SiMe2NR′)R″]+ of titanium catalysts supported by a linked amido-cyclopentadienyl ligand, several derivatives with different cyclopentadienyl C5R4 and amido substituents R′ were studied systematically. The use of tridentate variants (C5R4SiMe2NCH2CH2X)2− (C5R4=C5Me4, C5H4, C5H3tBu; X=OMe, SMe, NMe2) allowed the NMR spectroscopic observation of the titanium benzyl cations [Ti(η5:η1-C5Me4SiMe2NCH2CH2X)(CH2Ph)]+. Isoelectronic neutral rare earth metal complexes [Ln(η5:η1-C5R4SiMe2NR′)R″] can be expected to be active for polymerization. To arrive at neutral 12-electron hydride and alkyl species of the rare earth metals, we employed a lanthanide tris(alkyl) complex [Ln(CH2SiMe3)3(THF)2] (Ln=Y, Lu, Yb, Er, Tb), which allows the facile synthesis of the linked amido-cyclopentadienyl complex [Ln(η5:η1-C5Me4SiMe2NCMe3)(CH2SiMe3)(THF)]. Hydrogenolysis of the linked amido-cyclopentadienyl alkyl complex leads to the dimeric hydrido complex [Ln(η5:η1-C5Me4SiMe2NCMe3)(THF)(μ-H)]2. These complexes are single-site, single-component catalysts for the polymerization of ethylene and a variety of polar monomers such as acrylates and acrylonitrile. Nonpolar monomers such as -olefins and styrene, in contrast, give isolable mono-insertion products which allow detailed studies of the initiation process. |
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Keywords: | Single-site polymerization catalysts Polar monomer polymerization Alkyl complexes Hydride complexes Amido ligands |
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